"You know, Ruth," he said, "I don't wish to say anything against Isaac, and I don't want to make you uneasy, but you know as well as I do that he has a strange maggot in his brain.

There's a strange maggot hath got into their brains, which possesseth them with a kind of vertigo, and it reigns in the pulpit more than anywhere else, for some of our preachmen are grown dog mad, there's a worm got into their tongues as well as their heads.

Origin

Late Middle English: perhaps an alteration of dialect maddock, from Old Norsemathkr, of Germanic origin.

Around 2003 a photograph circulated on the internet purporting to show a man with maggots in the brain. The maggots were just an urban myth—one story said that the condition resulted from eating the Japanese raw-fish dish sashimi; another that it resulted from swimming in water where parasitic fish could enter the urinary tract (the candiru, a small catfish of the Amazon basin, does occasionally do this). The scare was new, but not the idea. When the Gothic novelist Charlotte Dacre published Zofloya, or the Moor in 1806, with its plot of murder and a Satanic lover, a reviewer pronounced that she must be ‘afflicted with the dismal malady of maggots in the brain’. Maggot is probably an alteration of the earlier word maddock, meaning ‘maggot’ or ‘earthworm’, influenced by Maggot or Magot, pet forms of the names Margery or Margaret. Compare pie

Derivatives

maggoty

The mushroom man, for instance - who also sold dates, walnuts and the best olives I've ever eaten - treated me better after an epic row over maggoty porcini which secured the refund I was after and also attracted a small approving crowd.

A west Wiltshire informant tells me that as a child he was cautioned against picking maggoty blackberries, ‘because the fairies had weed on them.’

I wash the dirt carefully off their stems, slice away any maggoty flesh, and cook them in garlic and cream.